INVESTIGADORES
GIUSTO Norma Maria
artículos
Título:
Phosphatidic acid and polyphosphoinositide metabolism in rod outer segments. Differential role of soluble and peripheral proteins
Autor/es:
ILINCHETA DE BOSCHERO, M.G.; GIUSTO, N.M.
Revista:
BIOCHIMICA AND BIOPHYSICA ACTA
Editorial:
Elsevier Science Publishers B.V.
Referencias:
Año: 1992 vol. 1127 p. 105 - 115
ISSN:
0006-3002
Resumen:
The phosphorylation of endogenous diacylglycerol (DAG) and
phosphoinositides by tau-32PATP was studied in bovine rod outer segments
(ROS) selectively depleted of soluble or peripheral and soluble
proteins by treatment with moderate (100 mM) or low (5 mM) ionic
strength medium, respectively. DAG kinase activity was similar in
bleached and non-bleached ROS extracted with 100 mM medium, and amounted
to 70% of that observed in the corresponding non-extracted ROS.
Phosphatidic acid (PtdH) labelling in ROS extracted in the dark with low
ionic strength medium was markedly lower than in those extracted in
light. Thus, even when a major proportion of DAG kinase was associated
to the membrane, a soluble form also occurred. Most of the
membrane-bound fraction behaved as a peripherally associated protein,
its binding to the membrane being modified by light. Ir ROS extracted at
moderate ionic strength the labelling of inositides was similar to that
in non-extracted ROS. A marked enhancement in polyphosphoinositide
labelling was observed in ROS extracted in the dark with low ionic
strength. Alkaline treatment of ROS also produced inhibition of
polyphosphoinositide phosphorylation. A peripheral form of a type C
phospholipase, or a peripheral protein-mediated activation of a
particulate form thereof, is suggested. Labelled polyphosphoinositides
were more actively hydrolyzed in the light and in the dark plus GTP tau S
than in the dark-incubated membranes. The results of phosphorylation
experiments in membranes where differential extraction of the alpha
subunit of transducin was carried out suggest that alpha and beta tau
subunits may play opposite modulating roles in PtdH and
polyphosphoinositide metabolism.